Building NetBSD system: what is PIGSGZIP?

I look at the build.sh command line in the build logs on
http://releng.netbsd.org/cgi-bin/builds.cgi
and at least for HEAD and netbsd-6, one parameter is
USE_PIGZGZIP=yes
What is this, and would it make a build succeed that would otherwise fail?
I just used the search on netbsd.org and found what it is, but how would it
affect a system build?
I see /usr/bin/pigz is in NetBSD base system but not FreeBSD; however pigz is
listed in archivers for both pkgsrc and FreeBSD ports.
Tom